Secretion and activity of histamine and serotonin during cold adaptation

¹ Department of Physiology, School of Medicine, Laval University, Quebec City, Canada

The urinary excretion of histamine was found to rise rapidly in rats exposed to cold (6 C). A sevenfold increase above normal is maintained during the 1st month of exposure, but during the 2nd month a decline from these high values is observed, and after 1 year the urine histamine is within normal limits. Similarly, a marked increase in the number of mast cells in the abdominal skin is observed during the first 2 months of cold exposure with a return to initial values by the 4th month. The blood pressure response to intravenous histamine is decreased during the 1st month of cold adaptation but after 1 year in the cold normal sensitivity to histamine is re-established. The excretion of 5-hydroxytryptamine is also rapidly increased during cold adaptation but no decline with time was observed. These findings obtained with histamine are compared with those found previously with noradrenaline. Whereas the urinary levels of these amines show similar variations during cold adaptation, the cardiovascular response differs. The sensitivity to histamine is decreased with increased excretion and the response to noradrenaline increased with increased secretion.